Question

Give a reason.
A. Annealing process is carried out in glass manufacture.
B. Vinyl plastic is used in preparing safety glass.

Answer 1

Hint: Annealing is the process to make the glass stable for the long term in finished form. Glass has an effect on temperature variation due to which stress is developed. Safety glass is a glass with additional safety measures.

Complete step by step answer:
(A) We know that annealing is a process by which glass is made stable in finished form. Annealed glass doesn’t break as long as it is subjected to an outside force.
One of the most distinctive properties of glass is its reaction to temperature variation. Glass on heating expands and on cooling it contracts. These processes create stress inside the glass, between the interior which can lead to break rage at room temperature.
So it is necessary to cool glass in a controlled manner through a predetermined temperature gradient. This allows the surface and the interior to cool uniformly. This controlled process for cooling glass to relieve internal stress is called annealing.
So annealing of glass is carried out to relieve internal stress introduced during manufacture.
(B) Now safety glass is a kind of glass that is less likely to break. It includes toughened glass and laminated glass. Vinyl plastic is used in such glass to make it tough and when it breaks it does not fly into pieces as vinyl plastic holds back the broken piece of glass.

Note: Glass is a supercooled liquid. When it is placed in the kiln for annealing it is held at a working temperature just to stop its molecules from flowing around one another. Then it is cooled slowly and it becomes stable.